Earth exceeding “safe operating” limits

A study of nine key processes that are critical for maintaining the stability and resilience of Earth’s health has revealed that in all but three we are already outside the “safe operating space for humanity”


Safe 	Boundary 	High-risk

Safe zone: Holocene period conditions during which agriculture and modern civilisation evolved

Interdependent systems affected by anthropogenic activities. Mitigating one can improve others – but quantifying this remains a challenge


1 Biogeochemical flows 
Fertilisers into soil and water

Phosphorous
Boundary: 11Tg* 
Current: 22.6Tg

Nitrogen
62Tg
190Tg


2 Freshwater flow change

Blue – rivers and aquatic ecosystems 
Boundary: 10.2% 
Current: 18.2%

Green – held in soil
Boundary: 11.1% 
Current: 15.8%


3 Land change

Forest cover
Global average boundary: 75% 
Current: 60%


4 Biosphere integrity

Functional Photosynthetic energy and materials flow


5
Sea pollution

Ocean acidification increasing


6 Air pollution 

Atmospheric aerosol load increasing


7 Stratospheric ozone 

Recovering after global ban on CFCs in 2010


8 Climate change

CO2 concentration
Boundary: 350ppm** 
2023 level: 417ppm

Radiative forcing
Boundary: 1 W/m2*** 
2022 level: 2.91 W/m2


9 Novel chemicals

Introduced by humans, e.g. CFCs, plastics
Upper limit unknown


Genetic
Boundary: <10 Extinctions per Million Species Years
Current: >100 E/MSY 


*1 teragram = 1 megatonne
**ppm = Parts per million
***W/m2 = Watts per metre squared


Source: Science
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